1. Field of the Invention
The present invention relates to a system, a method and program storage device readable by a machine, tangibly embodying a program of instructions executable by the machine to perform the method of providing UMS service using VoIP for providing unified messaging system (UMS) service using a voice over Internet protocol (VoIP).
2. Description of the Related Art
A unified messaging system (hereinafter, referred to as “UMS”) is an advanced technique based on existing E-mail and voice mail system (VMS) techniques and is a system designed to accommodate and collectively manage all media used in communications. It is also a system capable of collectively managing and operating automatic response system (ARS) service, VMS service, E-mail, facsimile (FAX) and the like in one system.
Accordingly, the UMS should include a public switched telephone network (PSTN) interface for a telephone network service, such as an automatic response system (ARS), a voice messaging system (VMS), a facsimile and the like, and an IP interface for connection to a packet network for an Internet messaging service, such as E-mail and the like.
In the public switched telephone network (PSTN) known as a telephone network, voice is generally delivered using pulse code modulation data or PCM data sampled at 64 kbps. Generally, in the voice communication, data is generated in real time and accordingly a method of transmitting the data should transmit the data in real time so that communication with a correspondent party listening to a relevant voice is smoothly made.
In the telephone network, such real time capability is always assured due to the characteristic of a circuit network that the network uses an allocated fixed bandwidth. The delay or loss of sound quality caused due to the limited bandwidth is always constant, and the users can communicate in the sound quality corresponding to PCM data of 64 Kbps.
Meanwhile, the development and rapid popularization of an Internet technique shifts a communication service base to an Internet base. A voice over Internet protocol (VoIP) is a technique for a series of equipment that delivers voice using an Internet data network. Therefore, there is an advantage that a variety of UMS services can be provided to all users connected to the Internet network when the UMS is implemented using the VoIP technique.
Generally, in the VoIP, voice information is transmitted in a digital form within discrete packets because the VoIP is not a traditional protocol based on a line like the PSTN. Thus, the introduction of a VoIP technique, which is a technique for transmitting the voice to the packet network, causes the loss of sound quality due to delay, jitter, and loss by the characteristic of the packet network. That is, there occurs a problem in that the distortion of the voice due to delay or loss becomes serious in view of characteristics of the packet network when PCM data is transmitted as it is in spite that the voice data should be transmitted in real time to a destination due to characteristics of the voice data. Consequently, the VoIP compresses and transmits the voice data at the rate of about 6.3 kbps or 8 kbps according to the type of a codec so that it is insensitive to the delay and loss of the packet to a certain degree.
However, there is also a problem in that the voice quality is further deteriorated due to the additional loss of the voice quality caused in the process of compressing the voice data to transmit the voice data to a packet network having a limited bandwidth.